Shotgun barrel and choke



Nov. 10, 1953 s. G. OBERFELL SHOTGUN BARREL AND CHOKE 2 Sheets-Sheet 1 Filed Feb. 27, 1950 INVENTOR.

G. G. OBERFELL BY 2 A TTORNE VS 1953 G. G. OBERFELL 2,658,298

SHOTGUN BARREL AND CHOKE Filed Feb. 27, 1950 2 Sheets-Sheet 2 INVENTOR.

c, c. OBERFELL gr-M A 7' TOR/VEYS Patented Nov. 10, 1953 NI TED "JQFEICE FS'HOTGUNv :BARREL AND GHOKE George GI'Obe'rfell, Bartlesville, "Okla.

Ap lication February 27, -1950,SerialNo.1465558 This .r invention J relates Ito -improvements in shotg1inbarrels. Inoneispecificaspect it relates -.to "shotgun -barrels having chokes; P In another '-,,s'pecific aspect it relates-to improved choke sectionsrfor shotgun barrels.

'r-In the prion art'of shotguns 'sometimes called "-:=scatter;guns', itwasiound thatwith-atrue cylinde1 b()1e":that' n-the' 'shotj :pellets become: unduly I: scattered at-:5 an arbitrary distance: of 4'0 Pyards.

I In -order to :reduce this scattering the inventors in the. prior art have: attached to,- or' -bui-lt into the shotgun-barrel, afichoke section having-a tapered :bore *of decreasing" diameter toward the -muzzle. -.'I l-1'ese shotgun bores having chokes'ections of thewprior art reduce the scatteringof the: shotat 40 yards -but do .:-so by'nndulyl concentratingthe shotpellets in the center of 'the pattern. The. pattern of the perfora-tions on a target at-40 yardsproduced by the shot-pellets of a shotgun charge fired through-ashotgun-barrel containing a 'conventional choke --shows =many void-spaces known as-patches, of an-arbitrary diameter of *5 inside 'ofa 30' circle, which last circle is drawn so =-as :toinclude the maximum number of: perforations. Each -'0f thesepatches.

represents a placewhere-a duckror-other game animal could be located within-l5" of-the center i of the-shot pattern andstill escape-Without critical injury. This is due=toan---uneven-distribution of the-pellets: over-the 30 diameter patternwith-an undueconcentration of pellets in or-near the central portion 'andmany"void patchesvor almost voidareasin various portions of the 30" pattern, especially in the outer: portions thereof.

This results a gameanimal-in-one portioncof the. pattern-where rthere is-a clustering-on pellets being filled with an excessive-number:of-:shot, which reduces its value for-food; whereas another -game animal located::at -adifferent point-in the pattern may escapernnwounded,-or may not be '"critical-l -vrounded andmay escape in a crippled condition.

Attempts have-been made in the -prior art-to counteract this tendency of the choke to concentrate' the 'shot'in' the center of the pattern by I riding the I choke section? with; helical; grooves, but such rifiing has proved :inefiectiveebcause it sets the shot chargeas at-body inrotationabout (the longitudinalaxis: of the shotgunbarrel;and-when -theshot charge emerges from -the muzzleof-.the:

shotgun. the individualpellets thereof spread rapidly-in alldirections. due to centrifugalforce.

:Inthe prior art,=-asthechoke was-increased decreasingxthe smallest =.-di'ameter. ofathe bore of the choke section, the percentagerof-npellets inthe targetnincreased up to -.a..maximum :after which further increase in the chokeresulted in: a scattering rinsteadlot-a further concentration of pellets.

I- have found that-by providinga shotgun chbke -having a bore generallyitapering.towaidthelinnz- 'zle and of reduced Idiameterv fromgthei bore of the shotgun. barrelvwith aplurality of-transverse J, grooves. in I its wall. of. said reduced idi'a'meter, .the

5 pelletsi'inthe. shot charge. passing lthroughl'this bor.e,--wh'ich contains depressions and elevations provided. by said transverse fgrooves, are/so agitated l'that -they are. evenly distributed in. a pattern, arbitrarilyibf"30". diametr,\ at a suitable "range, arbitrarily r-taken as40 yards. AlsoCthe pattern leni'ci'ency, .e., percentage 'of itheJpellets in the 'shoti'charge, placedin the' 30" diameter target, is increased over 'th'at obtained'iwith" the same diameter chokes of the prior art.

One object islto, provide .an improved-choke for shotguns.

- Another-object is to increase -the.uniform ity of distribution of shot pellets in'iflight as evidenced "by patterns made in paper targets ofarbitrary 20 diameter at arbitrary-ranges.

Another object is to reduce thenumber of game animals which escapefbeing killed, which are crippled and escape, 'or which are illledw-ith excessive numbers of shotpelle'ts.

Another obj ect is .to' provide improved shotgun chokes made "by simple and inexpensive mass productionmethods.

Another object is to provide: shotgun chokesiof simplebut improved design which. are inexpen- 30"sive,'ea'sy to. produce,- rugged, and whichfwill concentrate the shot p'ellets in the shot. pattern "with'iiniformdistribution of the shot'over-a limited diameter '.of pattern, but without local concentration of 'shotiiinfthe.pattern..with resulting void portions, on patches, of any substantial diameter.

Another object is to increase Jthe. pattern. efficiency, i.. e.,. the number 01: percentageof: pellets of .the shot charge. placed rin the target -by -the 40,.gun.

. Numerous otherobjects and-advantages will beapparentto-those skilled intheartlupon reading the accompanying specification, claims and drawings, in which:

"Figure. 1 is an. elevational cross-sectional view .of a shotgun embodying the' invention, with parts broken away.

Eigurez is an elevational.cross-sectional view not a por'tion of-Ithemuz'zleof ai shotgun. showing .one imodifid form, of. choke embodying imy invention.

Figure- 3. is a cross-sectional view.- of the struc- .ture shown in Figure- 2. taken alon-gthe line 3 3 looking. in the'direction indicated.

Eiguref Lisa.quarter sawed elevational view of another modificatien :01? a shotgun-chokeembodya'n g. anothen-inodification. ofItheinv-ention.

- Figure 5- is an elevational view. oi the, pattern made on a target by.plletsiromashotgunhaving one type of conventionalrchokesofithe .prior art, with circles drawn to aid in the study of the distribution. of the pellets.

Figure 6 is a view similar to Figure but taken of a representative pattern resulting when a shotgun choke embodying the present invention is used.

In Figure 1 a conventional shotgun generally designated as I is provided with a choke section generally designated as 8, which choke section embodies the present invention. This choke section may be an integral part of the barrel 9 of the shotgun as shown in Figure 1, or may be a separable extension generally designated as I I in Figure 2.

Shotgun I as shown in Figure 1 is entirely conventional except as to choke 8. It consists of a barrel 3 having one end sealed by breach block I2 which contains a firing mechanism (not shown) which may comprise a hammer I3. A conventional shotgun shell I4 comprises a base I6, having a percussion cap or primer I'l, powder charge I 8, powder chamber I 3, wads 20, 2! and 22, shot charge 23 front wad 24, and container 23. Container 23 is either crimped at 21 to retain front wad 24, or 21 is folded in some manner (not shown) in front of shot 23, in which case front wad 24 may be eliminated.

Shotgun barrel 9 has a bore comprising a chamber 23, a connecting conical portion 29, a

substantially cylindrical bore 3!, and a choke section 8. As all parts are conventional and well known to those skilled in the art, except the muzzle choke section 8, further description of the other parts of the shotgun is unnecessary.

In Figure 1, choke section 8 is formed integral with barrel 9 in the following manner:

Barrel 9 is preferably provided with a frustumshaped conical bore 32 of decreasing diameter toward the muzzle. While bore 32 may have a convexly and/or concavely belled taper (not shown) and still embody this invention, a plain conical taper is preferred. Ihe taper of bore 32 may vary considerably, and I have found that the conventional amount of taper in Shotgun chokes is satisfactory with the present invention, that shown in Figure 1 being representative. However. Figure 1 should be regarded as illustrative and not as limiting as to degree of taper, or shape, For example, many conventional chokes of the prior art have a cylindrical bore known as the parallel (not shown) of the same diameter as the muzzle end of conical bore 32 and following the same. Grooves similar to 33, 34, 33 and 3'! may be cut solely in said parallel, although it is preferred to out at least some or all of these grooves in the conical portion where they are more exposed for contact with the pellets of shot.

In the wall 32 of barrel 3 there is cut, preferably by a tool in a lathe or boring machine (not shown), a plurality of transverse annular circumferential grooves 33, 34, 36 and 31, leaving intermediate land surfaces 38, 39 and the like. The grooves and lands constitute alternate adjacent depressions and elevations in the bore of the gun barrel in Figure l, or in the bore of the choke tube in Figure 2. A plane passing through the gun barrel and lying parallel to the edges of the lands and the grooves would also be at right angles to the longitudinal axis of the gun barrel. lhe edge or boundary between the grooves and lands may be sharp or rounded. Thus, in addition to providing enlarged bores at 33, 34 and 36 for the pellets 23 to expand into, there are also provided transverse shoulders 4|. With eith sharp or rounded edges which agitate the pellets 23 and force the same back into bore 32 in the land portions 33 and 39 thereof. The number of such grooves, the width, depth and distance between the grooves may vary considerably with somewhat similar results. However, I prefer to use a groove width for grooves 33 of from onehalf to ten times the diameter of pellets 23, and while lands 38 can vary from the grooves in width, I prefer to have them substantially the same width as grooves 33. While the number of grooves 33 can vary, I prefer from 2 or even preferably 3 to 20 grooves, a plurality giving distinctively superior results to a single groove, particularly when the length of the grooved section of the barrel is from one to three times the length of the body of the shot charge of the shotgun cartridge. The grooves 33 preferably are from .02" to .001" in depth. Very successful results were obtained with 6 grooves such as 33, each groove being .003" deep and A; wide separated by lands such as 38 each A;" wide. As the grooves are made shallower than .001" there is less beneficial eifect, but they can be deeper than .02, but such additional depth does not provide essentially better disposition of the shot.

In Figure 2 the choke I I is provided as a separable tube 42 which is secured to the end of shotgun barrel 43 by any suitable connecting means such as the threaded coupling 44, or by a bayonet-joint type of connection (not shown). Obviously, choke 8 of Figure 1 could have been made separable and so secured to barrel 9.

In Figure 2 choke II is provided with a frustum-shaped conical bore 46 of decreasing diameter toward the muzzle 41. The taper is more pronounced than in Figure 1, but any taper used in prior art shotgun chokes is satisfactory. Tube 42 may be provided with Wrench holes 48 to aid in attaching the same, and when present such holes act partly as a muzzle brake in reducing the recoil of the shotgun and act to relieve some of the pressure. However, holes 43 are not essential and may be eliminated.

Semi annular circumferentially disposed transverse grooves 49, 53 and 5! are provided, preferably with a plurality of such grooves in each transverse plane (such as plane 33) with the grooves in alternate planes being staggered to place grooves 49, 50 and El (for example) overlapping in echelon around the entire circumference of the choke II.

While the exact shape of grooves 49, 50 and 5i is not critical as long as substantially transverse shoulders 52 of sharp or rounded edges are provided and there are no helical elements tending to cause rotation of the shot charge which would scatter the same, economy dictates that grooves 49, 50 and 5| be made in a simplemanner.

As shown in Figure 3, possibly the simplest manner of making the semi-annular grooves such as 49, '50 and EH is by grinding or cutting the same in the wall 46 with a rotating circular cutter (not shown) of less diameter than corresponding portion of bore 46. This cutter (not shown) can be inserted longitudinally in bore 43 and then moved laterally back and forth in each transverse plane (such as 3-3) to cut the semi-annular grooves such as 49 and 50, and then removed.

Figure 4 shows a choke generally designated as 53 which is made in an inexpensive manner by stamping, but which may embody annular grooves such as 53 similar in effect to the groove 33 of Figure 1 and/or semi-annular grooves such as cacss'rees i 54, fifiiand'lz'fil similar iiniefiectiitox-grocvesdfizand Eibzof: Figureiaz. wFnr a'thespimpose:ofv illustration thea'semi-annulara grooves; are shownzascfdepresesions 'li, '561a'nd151 stamped iinithe zwalllifificoi choke 53, whil -"an;annularrgroovefiQnhas been r rolled or spunsn therwall58.

As depressions'i fi 4', 56 Elna-hellEBJinrEigureA are iormedrinficho'kejBarbyidefiormdng thezcnetal, there vzill be= bosses 5.6 I nor ridgesetzoon: thee-exterior of choke 53 whichihavesaneattractivel design appearance :of advertising value. rHoles I laxare the samesas finliFligurez 2; andrlthreaidsz fi3 are similar -toithoseengaging coupling Eigure].

"'It will be clearly seen byview-mgitheitapered portion 8 inZFig-ure: lLthat theia-ngle otdihashoul- 'der 4 i fo rmed:betweertthei'wall formingztheoutlet end-side of ."each- -zgroove 33,234,; ssandi therespectiveadjacent Elana- 38339 :in athe-zfdirection of the outlet end of chokex The corresponding 1 shoulder 52cin Figure: 211s :also obtuse. The corresponding :shoulder: EQEimsFigure 4-iseven more obtuse; becausetofathe beveled slope caused by stamping;rollingmrsspinningz the *6 adiametencircle: Maia-drawn to-zinclude: the maxiimummumberr of.: pelIete-holes .-fi6. A: concentric :zinnerc circle :61 3.:ofo20" diameter aidssin evalurating the; results; Because. of @the- @undue-i conscent-rationsotshotrby the/conventionalchoke in the centralrportion Or -the. pattern around such ;=.;.points-zasc 68, iitherez are :void: 'areasssurrounding widelyspacedf. single' zshot such :as- 66, and there arexazlarge mumbers of --completely void areas 10 -.;'(aknown-: asspatches) i-of: Jan arbitrary diameter of 5.! as :indicated by 5 diameter: circles 69.

rz-l figure'ceshows the improvedresults of :the present invention on as'target ofrthesame diamdeter mat lithe: same range-rand aundsr conditions similar ato ithoseainvolved ixinrEigure 5. When metal as visible in the'drawingaandexplained in :2

r the second paragraph :preceding. 'T-his =1 obtuse angle approachesa 'righti'ianglezzaszarlower limit eand does not include.acutevangleeias obviously acute angles will cutintoithespassingshotpellets.

In any "of Figures 12 to .4. it .is :entirelysatise factory to mix both: annular: 'andrsemi-eannular grooves, or use them separately; "with roriwithout overlapping, butbest overi-allrresultseas" to'reconomics ofv manufactureiattractive appearanceof the article 'in commerce, candxsimilar iactors,

make it preferable to haveiall the'groove. elements similar, and theoretically there? should"bercomplete overlapping of Igrooves iaaround J the :entire circumference in order that the shott'chargevwill be uniformly treated'inipassingiithrongh' the bore 'of the ch0ke, which--uniform treatment .should aid in attaining-"uniform distributionzof:thershot "in the pattern.

Although Figures .1': to 4E'it is; not :necessary to have exactly itransverse :circumferential *grooves; nor need i the entirerextenttofi anyigroove be transverse, the type:of :depressionsr torielevations provided in the boreoofs"thdguhwshOuld be such as to avoid impartingza rotating EmOtlOIl Of the body ofthe'=shot-chargeraround the---long-i tudinal: axis of theigun ubore, asi'iszimpartedtto a rifle bullet as :it ipassesithroughzthe 21113110311 groovesof a rifle. -;If-:a helicallor slanting-pertion- (not shown) of one; grooveashouldcimpart such rotation to a'pellet -it is-. prefer-red 'thatthe 113811813 be subjected before leaving the muzzle to a a like impulsein-the opposite direction by an oppositely disposedrhelical or slanting portion. Obviously it is preferablenot to"have"any such helical or slanting, grooves;'orportions"'of r, grooves; but 'theymaybeemployed provided they are so disposed"that"their'net-effectis "that=-'-of transverse circumferential "grooves.

Figure 5 shows a pattern shot into a paper target at '40 "yards -using-'--a conventional chbke of the prior-art. This"-pattern1 isrworserthan would be expected from a pattern v10f '127ipellets according to Table 1 and,-therefore;tis not repre sentative of the: prior art,; but is:chosenobecause it' illustrates the :uneven: distribution ofssh'ot very clearly. Patterns which are-representative of thezprior art arediscussed==belowan-d are tabulated infiTables 1 andr2. -'I'-hey.- alsorhad-. .uneven distribution: of the type shownr-inz-Eigure: 5, .al-

:ithoughi it wasnot sorevident. lnz'Eig urei-5; a;:30'

sBil'ClGS: 54::and5 GLzare 2 drawn, it is "seen that the gi'pelletsififi aregquite? evenlyrdistributed, thatthere :lSnnO ,und-ue: concentration., of peilets such; as at sa -of-Figurefi and thatthere are'not patches 69. Figure 6 1 regarded as representative :of wthe results-to be expected with the present invention.

EXAMPLE iL-haveaanalyzed many a shotgun patterns for 5 :the purpose of .determining the patchiness of a such patterns. Using as a measure of patchiness the numberof pellet-hole-fre'e circular a-reasiwith a I diameter of fiveinches within the pattern, 1 I Zhave found that the-average patchiness of "shotgun patterns using the conventional shotguns, shotgunchokes,- shotgun shells, and shotgun pellets. of the prior art "which :are obtainable on the open market, will be substantially :as shown inthe-example, Table -1, which-follows.

"TABLE 1 Relation between the mm'tbcr ofv pellets and the number of.se'paratef5- inch diameter circular paichesiin30-inch patterns produced by guns andchokes' offthe prior art pellets patches pellets patches pellets patches 2.25 -22 125 7 i 225 2 "'17 150 5 2-50 1 '75 V l2 -175 4 275 1 100 9 200 3 $300 0 The "*relation between the number or pellets 50 and the number of'patchesinBO" shotgun pat- "terns as shown in'the tableimmedlatelyabove 'iepresents the-average'results of numerous tests involving a large number of variables such as:

-' different'guns; different' gauges of guns, difierent 5 sizes of shotyshotgunshells of difierentammunition manufacturers, different powder charges, different chokes, choke devices of different'manw facturers, as well as difierent weather and clizznatic conditions; .ieAlthoughi'itheztable1serves as a good-guidefor:patchiness?expectations,. control the 20 circle, and only 49 pellets between the 20" and 30" circles. In'Figure 6 where the "present: invention'is used there are 178 pellets inside the 30" circle of which'88 pellets are inside the 20" circle and 90 pellets-.areibetween the circles, a substantially, even distribution. The

I evenly (forshot pellets) over the entire surface:

I I second bad effect in Figure is that thepellets I I 1 in passing through I the barrel of the shotgun I I I and chokes of the priorarttend to weld or stick 1 together, and while brokenapart again by air :resistance, little closely spaced groups of the pellets still tend to appearin thepattern, with I 1 the; resulting void areas, or patches 69, being 1 1 I v 1 increased innumber. As shown in Figure 6, my I invention, tends to eliminate both of these 'undesirable: effects and distributes the shot quite 1 insidethe 3.0" diameterring' 54 as the 20," diameter ring Bl.

I reducing: the tendency of the charge of pellets I 1 I I. have. experimented: with several mechanical I I I 1 I means having for their objective preventing or 1 v to ball orweldtogether as it passes through the 1 I 1 various portions of the gun, including thechoke. I I

through the; bore of the gun, will undergo ex 1 cessive scattering of pellets before :they. reach 1 the'target; This scattering eiiectcan be lessened I in the bore of the: barrel or in the :bore of the obtain many other manner.: I have analyzed,

; :gIf the bore of the shotgun contains :grooves as 1 I 1 does a rifle, the'charge'of pellets,1,after1it passes I Explanations-The new choke tube for test I 1 1 1 No; I was purchased in the open market from a I I I I 1 1 manufacturer of choke devices;

conducted with a duplicate new choke tube from I the same manufacturer, except that the choke I tube for test 'No; 2 had been provided with: 6

circumferential grooves. wide and .003 deep I spaced: apartv in the manner shown in Fig- TestNo. 2 was ure 1, although the: choke tube was detachable as shown in Figure 2 at 4'4. 1 I

' The ordinary shotgun cartridges or shotgun shells which are'obtainablethrough the regular I 1 I 1 channels oftrade, when'used with my invention,

will produce better, more even and more regular patterns, with less 5 diameter patches, or less 1 1 1 void spaces of any considerablearea.

1 While I' have described andshown :abovecen:

tain'modifications embodying my invention and 1 i for purposes of illustration and have given the i result of representative tests in order to, explain the invention; such disclosures should not be 1 1 regarded as limiting the 1 scope of the invention I I I I i 1 which is defined by the following I I I claim as myinvention: f 1 W 1. A shotgun choke comprisingin 1 a tube having'a' bore, said: borehaving an inlet claims. I

combination end; and an outlet; end for shot pellets, a portion 1 choke tube, I obtain a very much better and I I 1 less patchy pattern than .I have been able to I I the most even distribution: of pellets were 010- 1 1 tained with a chokedevice containing such cirxcumferential grooves as shown in F gure 1; 1 The two patterns compared below in Table 'No. 2 are representative and were made with the same 12-gauge gun firing shells from the same box purchased on the open market. These shells contained 3% drams of powder and 1 ounces of No. 6 shot (about 275 shot each, more or less). A pattern was made on targets yards distant from the muzzle of the gun. In test No. 1 below, a conventional choke was used, and was representative in producing a pattern with 4 patches. Figure 5 does not show the target of test No. 1, but shows instead a considerably worse pattern with 10 patches 59, being only used for illustrative purposes. Figure 6, however, is an accurate scale reproduction of the representative pattern obtained in repre- I sentative test No. 2 when employing the present invention.

TABLE 2 Numerical analysis of patterns of shot pellets fired from shotgun with choice tubes Test No. 2 with new full choke tube with circumferen tial grooves Test No. 1 with new full choke tube with a smooth bore Control Control iii) of said bore i being tapered with a decreasing I I I I i diameter in the direction: of said outlet end to L L choke said shot, said tube being: adapted to be 1 I I disposed with its inlet end aligned with and com I I I I I municating with themuzzle of a shotgun barrel to 'form a 'continu'ation thereof' of initially the 1 same internal diameter, the walls of said tube I I I I I I formingthe decreased diametertapered portion ,1 1 pi said bore being formed with alternate trans-' verse lands and transverse grooves'in which the 1 I 1 I 1 1 angle of the shoulder formed between the wall I formingthe outletiend side of each groove and I I I I the adjacent land in the direction ofsaid outlet 1 I 1 I 1 'en'd'is an obtuse anglewhereby shot pellets fired through said bore of said choke are agitated without undue deformation by alternate expansion of some of said pellets into said grooves and contact with said shoulders.

2. The combination of a shotgun having a barrel and a shotgun choke forming a continuation of the muzzle end of said barrel of initially the same internal diameter, said shotgun choke comprising in combination a tube having a bore, said bore having an inlet end and an outlet end for shot pellets coming from said shotgun barrel, a portion of said bore being tapered with a decreasing diameter in the direction of said outlet end to choke said shot, said walls of said tube forming the decreased diameter tapered portion of said bore being formed with alternate transverse lands and transverse grooves in which the angle of the shoulders formed between the wall forming the outlet end side of each groove and the adjacent land in the direction of said outlet end is an obtuse angle whereby shot pellets fired through said bore of said choke are agitated without undue deformation by alternate expansion of some of said pellets into said grooves and contact with said shoulders.

3. The combination of claim 1 in which the grooves are from .02 to .001 inch deep.

4. The combination of claim 1 in which the grooves are annular.

5. The combination of claim 1 in which the grooves are recessed into the wall of the choke and the exterior of the choke is cylindrical.

6. The combination of claim 1 in which the 9 walls of the choke are displaced outwardly at the grooves.

2'. The combination of claim 1 in which the transverse grooves are semi-annular with a plurality in one transverse plane.

8. The combination of claim 1 in which the grooves lie in a plurality of transverse planes with the grooves in one transverse plane overlapping 1n echelon the grooves in a second transverse plane.

9. The combination of claim 1 in which the grooves are recessed into the wall of the choke 10 and the exterior of the choke is cylindrical and said grooves are semi-annular.

GEORGE G. OBERFE'LL.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 785,975 McClean Mar. 28, 1905 1,342,978 Young June 8, 1920 1,352,938 Blair Sept. 14, 1920 2,167,173 Fleming July 25, 1939 2,315,207 Janecek et al Mar. 30, 1943 

